Active inductor implementation in a communication system

Abstract

An example apparatus as discussed herein includes a first communication circuit and a second communication circuit. A communication link couples the first communication circuit and the second communication circuit. The communication link conveys signals between the first communication circuit and the second communication circuit. The first communication circuit includes a first active inductor set to a first inductance; the first inductance controls a resonant frequency (carrier frequency) of communicating signals from the first communication circuit. The second communication circuit includes a second active inductor set to a second inductance. The second inductance controls a frequency response (such as band-pass resonant frequency) of a band-pass filter in the second communication circuit. The setting of the first inductance and the second inductance aligns the resonant frequency of the transmitted signals with respect to a peak or center frequency passed by the band-pass filter.

The invention claimed is: 
     
       1. An apparatus comprising:
 a first communication circuit including a first active inductor set to a first inductance, the first inductance controlling a resonant frequency of communicating signals from the first communication circuit; 
 a second communication circuit including a second active inductor set to a second inductance, the second inductance setting a frequency response of a band-pass filter in the second communication circuit; and 
 a communication link coupling the first communication circuit and the second communication circuit, the communication link operable to convey the signals between the first communication circuit and the second communication circuit. 
 
     
     
       2. The apparatus as in  claim 1 , wherein a setting of the first inductance aligns the resonant frequency of the signals with respect to a center of the band-pass filter. 
     
     
       3. The apparatus as in  claim 1 , wherein the first active inductor is fabricated to provide the first inductance value via trimming of at least one component in the first active inductor, the first active inductor controlling a resonant frequency of transmitting the signals over the communication link; and
 wherein the second active inductor is fabricated to provide the second inductance value via trimming of at least one component in the second active inductor, the second active inductor controlling settings of the band-pass filter disposed in the second communication circuit. 
 
     
     
       4. The apparatus as in  claim 1 , wherein a length of the communication link disposed between the first communication circuit and the second communication circuit is less than 5 inches. 
     
     
       5. The apparatus as in  claim 1 , wherein the first inductance of the first active inductor defines a resonant frequency of a transmitter of the first communication circuit coupled to the communication link; and
 wherein the second inductance of the second active inductor defines frequency settings of the band pass filter in the second communication circuit, the apparatus further comprising: 
 an envelope detector operative to convert a filtered signal received from the band-pass filter into an output signal, the output signal being a replica of an input signal inputted to the transmitter of the first communication circuit. 
 
     
     
       6. The apparatus as in  claim 1 , wherein the second inductance is substantially equal to the first inductance; and
 wherein the second active inductor is configured in a same manner as the first active inductor. 
 
     
     
       7. The apparatus as in  claim 1 , wherein the first active inductor includes a first set of transconductance amplifiers operative to provide the first inductance; and
 wherein the second active inductor includes a second set of transconductance amplifiers to provide the second inductance. 
 
     
     
       8. The apparatus as in  claim 1 , wherein the first communication circuit and the second communication circuit are coupled to a common substrate. 
     
     
       9. The apparatus as in  claim 1 , wherein the first communication circuit and corresponding circuit components including the first active inductor are galvanically isolated with respect to the second communication circuit and corresponding circuit components including the second active inductor. 
     
     
       10. The apparatus as in  claim 1 , wherein the first communication circuit is a first transceiver operative to transmit/receive signals over the communication link; and
 wherein the second communication circuit is a second transceiver operative to transmit/receive the signals over the communication link. 
 
     
     
       11. The apparatus as in  claim 1 , wherein the signals are differential signals; and
 wherein the communication link includes a pair of conductive paths extending between the first communication circuit and the second communication circuit, the pair of conductive paths operable to convey the differential signals. 
 
     
     
       12. The apparatus as in  claim 11 , wherein the pair of conductive paths includes a first conductive path and a second conductive path extending between the first communication circuit and the second communication circuit; and
 wherein the first inductance and the second inductance are disposed in series along the first conductive path. 
 
     
     
       13. The apparatus as in  claim 12 , wherein the first communication circuit includes a third active inductor set to a third inductance;
 wherein the second communication circuit includes a fourth active inductor set to a fourth inductance, the fourth inductance substantially matched to the third inductance; and 
 wherein the third inductance and the fourth inductance are disposed in series along the second conductive path. 
 
     
     
       14. The apparatus as in  claim 1 , wherein the first communication circuit is fabricated on a first semiconductor chip; and
 wherein the second communication circuit is fabricated on a second semiconductor chip. 
 
     
     
       15. A method comprising:
 coupling a first communication circuit and a second communication circuit to a communication link, the communication link operable to convey signals between the first communication circuit and the second communication circuit, 
 setting a first inductance of a first active inductor disposed in the first communication circuit, the first inductance controlling a resonant frequency of communicating the signals from the first communication circuit to the second communication circuit; and 
 setting a second inductance of a second active inductor disposed in the second communication circuit, the second inductance setting a frequency response of a band-pass filter in the second communication circuit that receives the signals. 
 
     
     
       16. The method as in  claim 15 , wherein a setting of the first inductance aligns the resonant frequency of the signals with respect to a peak frequency passed by the band-pass filter. 
     
     
       17. The method as in  claim 15  further comprising:
 fabricating the length of the communication link disposed between the first communication circuit and the second communication circuit to be less than 5 inches. 
 
     
     
       18. The method as in  claim 15  further comprising:
 affixing the first communication circuit and the second communication circuit to a common substrate. 
 
     
     
       19. The method as in  claim 18 , wherein a magnitude of the resonant frequency of a transmitter communicating the signals is within 5% of a magnitude of a band-pass resonant frequency of the band-pass filter. 
     
     
       20. The method as in  claim 14  further comprising:
 providing galvanic isolation between the first communication circuit and the second communication circuit.